Influence of SPION Surface Coating on Magnetic Properties and Theranostic Profile.

This study aimed to develop multifunctional nanoplatforms for both cancer imaging and therapy using superparamagnetic iron oxide nanoparticles (SPIONs). Two distinct synthetic methods, reduction-precipitation (MR/P) and co-precipitation at controlled pH (MpH), were explored, including the assessment of the coating's influence, namely dextran and gold, on their magnetic properties. These SPIONs were further functionalized with gadolinium to act as dual T1/T2 contrast agents for magnetic resonance imaging (MRI). Parameters such as size, stability, morphology, and magnetic behavior were evaluated by a detailed characterization analysis. To assess their efficacy in imaging and therapy, relaxivity and hyperthermia experiments were performed, respectively. The results revealed that both synthetic methods lead to SPIONs with similar average size, 9 nm. Mössbauer spectroscopy indicated that samples obtained from MR/P consist of approximately 11-13% of Fe present in magnetite, while samples obtained from MpH have higher contents of 33-45%. Despite coating and functionalization, all samples exhibited superparamagnetic behavior at room temperature. Hyperthermia experiments showed increased SAR values with higher magnetic field intensity and frequency. Moreover, the relaxivity studies suggested potential dual T1/T2 contrast agent capabilities for the coated SPpH-Dx-Au-Gd sample, thus demonstrating its potential in cancer diagnosis.

Metal mobility and bioaccessibility from cyanide leaching heaps in a historical mine site.

Unlike acidic sulfide mine wastes, where metal/loid mobility and bioaccessibility has been widely studied, less attention has been paid to alkaline cyanide heap leaching wastes. Thus, the main goal of this study is to evaluate the mobility and bioaccessibility of metal/loids in Fe-rich (up to 55%) mine wastes resulting from historical cyanide leaching activities. Wastes are mainly composed of oxides/oxyhydroxides (i.e. goethite and hematite), oxyhydroxisulfates (i.e. jarosite), sulfates (i.e., gypsum, evaporitic sulfate salts), carbonates (i.e., calcite, siderite) and quartz, with noticeable concentrations of metal/loids (e.g., 1453-6943 mg/kg of As, 5216-15,672 mg/kg; of Pb, 308-1094 mg/kg of Sb, 181-1174 mg/kg of Cu, or 97-1517 mg/kg of Zn). The wastes displayed a high reactivity upon rainfall contact associated to the dissolution of secondary minerals such as carbonates, gypsum, and other sulfates, exceeding the threshold values for hazardous wastes in some heap levels for Se, Cu, Zn, As, and sulfate leading to potential significant risks for aquatic life. High concentrations of Fe, Pb, and Al were released during the simulation of digestive ingestion of waste particles, with average values of 4825 mg/kg of Fe, 1672 mg/kg of Pb, and 807 mg/kg of Al. Mineralogy may control the mobility and bioaccessibility of metal/loids under rainfall events. However, in the case of the bioaccessible fractions different associations may be observed: i) the dissolution of gypsum, jarosite and hematite would mainly release Fe, As, Pb, Cu, Se, Sb and Tl; ii) the dissolution of an un-identified mineral (e.g., aluminosilicate or Mn oxide) would lead to the release of Ni, Co, Al and Mn and iii) the acid attack of silicate materials and goethite would enhance the bioaccessibility of V and Cr. This study highlights the hazardousness of wastes from cyanide heap leaching, and the need to adopt restoration measures in historical mine sites.

Redox and guest tunable spin-crossover properties in a polymeric polyoxometalate.

A bifunctionalized polyoxometalate (POM), [V6O19(C16H15N6O)2]2-, which contains a redox active hexavanadate moiety covalently linked to two tridentate 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligands, has been prepared and characterized. Reaction of this hybrid molecule with Fe(ii) or Zn(ii) ions produces crystalline neutral 1D networks of formula Fe[V6O19(C16H15N6O)2]·solv (2) and Zn[V6O19(C16H15N6O)2]·solv (3) (solv = solvent molecules). Magnetic properties of 2 show an abrupt spin-crossover (SCO) with the temperature, which can be induced by light irradiation at 10 K (Light-Induced Excited Spin-State Trapping, LIESST effect). Interestingly, this porous and flexible structure enables reversible exchange of solvents in 2, which allows tuning the temperature of the thermal SCO. In 2 and 3, the hexavanadate unit can be reduced by electrochemical or chemical means in a reversible way. Chemical reduction and reoxidation by a postsynthetic method is accompanied by the insertion in the structure of the reductant and oxidant molecules (cobaltocene and tribromide, respectively), which provokes drastic changes in the spin state of Fe(ii). This leads to an elegant switching multifunctional material in which SCO properties of the Fe(ii) complexes coexist with the redox properties of the POM and can be tuned by a variety of stimuli such as temperature, light, solvent exchange or electron transfer. During the reduction process, 3 undergoes a single-crystal-to-single-crystal one-electron reduction, which confirms the presence of cobaltocenium cations by single crystal X-ray diffraction.

3D-printed platform multi-loaded with bioactive, magnetic nanoparticles and an antibiotic for re-growing bone tissue.

Polymeric platforms obtained by three-dimensional (3D) printing are becoming increasingly important as multifunctional therapeutic systems for bone treatment applications. In particularly, researchers aim to control bacterial biofilm on these 3D-platforms and enhance re-growing bone tissue, at the same time. This study aimed to fabricate a 3D-printed polylactic acid platform loaded with hydroxyapatite (HA), iron oxide nanoparticles (IONPs) and an antibiotic (minocycline) with tuneable properties and multistimuli response. IONPs were produced by a facile chemical co-precipitation method showing an average diameter between 11 and 15 nm and a superparamagnetic behaviour which was preserved when loaded into the 3D-platforms. The presence of two types of nanoparticles (IONPs and HA) modify the nanomorphological/nanotopographical feature of the 3D-platforms justifying their adequate bioactivity profile and in vitro cellular effects on immortalized and primary osteoblasts, including cytocompatibility and increased osteogenesis-related gene expression (RUNX2, BGLAP and SPP1). Disk diffusion assays and SEM analysis confirmed the effect of the 3D-platforms loaded with minocycline against Staphylococcus aureus. Altogether results showed that fabricated 3D-platforms combined the exact therapeutic antibiofilm dose of the antibiotic against S. aureus, with the enhanced osteogenic stimulation of the HA and IONPs nanoparticles which is a disruptive approach for bone targeting applications.

SPIONs Prepared in Air through Improved Synthesis Methodology: The Influence of γ-Fe2O3/Fe3O4 Ratio and Coating Composition on Magnetic Properties.

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown great potential in biomedicine due to their high intrinsic magnetization behaviour. These are small particles of magnetite or maghemite, and when coated, their surface oxidation is prevented, their aggregation tendency is reduced, their dispersity is improved, and the stability and blood circulation time are increased, which are mandatory requirements in biomedical applications. In this work, SPIONs were synthesized in air through a reduction-precipitation method and coated with four different polymers (Polyethylene glycol(PEG) 1000/6000 and dextran T10/T70). All the synthesized samples were structurally and magnetically characterized by transmission electron microscopy, Fourier transform infra-red spectroscopy, X-ray powder diffraction, Mössbauer spectroscopy, and Superconducting Quantum Interference Device (SQUID) magnetometry. SPIONs centrifuged and dried in vacuum with an average diameter of at least 7.5 nm and a composition ≤60% of maghemite and ≥40% of magnetite showed the best magnetization results, namely a saturation magnetization of ~64 emu/g at 300 K, similar to the best reported values for SPIONs prepared in controlled atmosphere. As far as SPIONs' coatings are concerned, during their preparation procedure, surface polymers must be introduced after the SPIONs' precipitation. Furthermore, polymers with shorter chains do not affect the SPIONs' magnetization performance, although longer chain polymers significantly decrease the coated particle magnetization values, which is undesirable.

Naturally occurring radioactive material and risk assessment of tailings of polymetallic and Ra/U mines from legacy sites.

Old mine tailings from Northern and Central Portugal were studied in order to perform a radiological and chemical characterization. The evaluation of massic activity of natural radionuclides and concentrations in tailings of polymetallic and Ra/U mines was performed by gamma spectrometry and neutron activation analysis. Iron speciation was carried out by Mössbauer spectroscopy. In polymetallic tailings with physical ore processing (Cumieira and Verdes - exploited for Sn, Nb-Ta) higher contents of Th, 228Ra and 226Ra in the coarser materials occur, probably due to their presence in host rock and ore fragments. In finer tailings, washing may explain the lower 226Ra and 210Pb massic activity. In tailings with physical/chemical ore processing (Covas - exploited for W and Sn) high U contents and a tendency for higher 226Ra and 210Pb massic activity in the fine materials is observed, probably due to their incorporation in nano-sized particles of iron oxides. A high variation of the 210Pb/226Ra ratio occurs in polymetallic tailings; a deficit of 210Pb can be observed particularly in deposits of settling tanks drained from dumps of chemically treated ore. In Ervideira-Mestras tailings (Ra/U exploitation) where no ore process in situ was performed, a near equilibrium between 210Pb and 226Ra occurs. Dose risk assessment was carried out by calculating external outdoor Annual Effective Dose Rate; the dose rates in air due to terrestrial gamma radiation are low for the polymetallic tailings (<47 nGy/h), and higher for tailings of Ra/U (up to 4130 nGy/h), in the worst scenario.

Variable Dimensionality, Valence, and Magnetism in Fluoride-Rich Iron Phosphates Ba xFe x(PO4)F y (1 ≤ x ≤ 3, 2 ≤ y ≤ 12).

We report the synthesis and characterization of three fluoride-rich barium iron phosphates Ba xFe x(PO4)F y (1 ≤ x ≤ 3, 2 ≤ y ≤ 12), which exhibited abundant structural chemistry, exhibiting diverse frameworks and connecting modes between [FeO nF6- n] m- octahedra surrounding Fe2+ or Fe3+ ions. BaFe(PO4)F2 (I) consisted of two-dimensional [Fe(PO4)F2]2- sheets built from linear ∞[Fe2O6F4]10- moieties formed by fluorine corner-sharing FeO4F2 and FeO2F4 octahedra with linking PO4 tetrahedra. Mixed-valence Ba2Fe2(PO4)F6 (II) possessed a three-dimensional framework containing Fe4O6F12 tetramers formed by the edge-sharing oxygen or fluorine atoms of cis-FeF4O2 octahedra. Ba3Fe3(PO4)F12 (III) contained one-dimensional columns of ∞[Fe3(PO4)F12]6- infinite sections built from cis-FeF4O2 and FeF5O octahedra and tetrahedral PO4 linkers. The magnetic characterization of Ba xFe x(PO4)F y unveiled diverse magnetism: an S = 5/2 spin chain for (I), a weak ferrimagnet or canted antiferromagnet for (II) thanks to the presence of distinct Fe2+ and Fe3+ sites identified by Mössbauer spectroscopy, and coupled spin-trimers for (III).

Dynamically slow solid-to-solid phase transition induced by thermal treatment of DimimFeCl4 magnetic ionic liquid.

The results reported here represent the first direct experimental observations supporting the existence of a solid-to-solid phase transition induced by thermal treatment in magnetic ionic liquids (MILs). The phase transitions of the solid phases of 1,3-dimethylimidazolium tetrachloroferrate, DimimFeCl4, are closely related to its thermal history. Two series of solid-to-solid phase transitions can be described in this MIL: (i) from room temperature (RT) phase II [space group (s.g.) = P21] to phase I-a [s.g. = P212121] via thermal quenching or via fast cooling at T > 2 K min(-1); (ii) from phase I-a to phase I-b [s.g. = P21/c] when the temperature was kept above 180 K for several minutes. The latter involves a slow translational and reorientational dynamical process of both the imidazolium cation and the tetrachloroferrate anion and has been characterized using synchrotron and neutron powder diffraction and DFT (density functional theory) studies. The transition is also related to the modification of the super-exchange pathways of low-temperature phases which show a overall antiferromagnetic behavior. A combination of several experimental methods such as magnetometry, Mössbauer and muon spectroscopy together with polarized and non-polarized neutron powder diffraction has been used in order to characterize the different features observed in these phases.

Easy Excited-State Trapping and Record High TTIESST in a Spin-Crossover Polyanionic Fe(II) Trimer.

Reaction of the polysulfonated triazole ligand L = 4-(1,2,4-triazol-4-yl)ethanedisulfonate) with iron(II) salts in water yields the trimeric species [Fe3(µ-L)6(H2O)6](6-). This polyanion, as the dimethylammonium salt, shows a thermally induced spin transition above room temperature for the central Fe position in the trimer with a large hysteresis cycle (>85 K) and remarkably slow dynamics. This allows easy quenching of the metastable high-spin (HS) state via gradual cooling (5 K min(-1)). Once it is trapped, the HS state remains metastable. Thermal energy is not able to promote relaxation into the low-spin ground state below 215 K, with a characteristic TTIESST = 250 K, the highest temperature ever observed for thermal trapping of an excited spin state in a switchable molecular material.

Anion-π and halide-halide nonbonding interactions in a new ionic liquid based on imidazolium cation with three-dimensional magnetic ordering in the solid state.

We present the first magnetic phase of an ionic liquid with anion-π interactions, which displays a three-dimensional (3D) magnetic ordering below the Néel temperature, TN = 7.7 K. In this material, called Dimim[FeBr4], an exhaustive and systematic study involving structural and physical characterization (synchrotron X-ray, neutron powder diffraction, direct current and alternating current magnetic susceptibility, magnetization, heat capacity, Raman and Mössbauer measurements) as well as first-principles analysis (density functional theory (DFT) simulation) was performed. The crystal structure, solved by Patterson-function direct methods, reveals a monoclinic phase (P21 symmetry) at room temperature with a = 6.745(3) Å, b = 14.364(3) Å, c = 6.759(3) Å, and ß = 90.80(2)°. Its framework, projected along the b direction, is characterized by layers of cations [Dimim](+) and anions [FeBr4](-) that change the orientation from layer to layer, with Fe···Fe distances larger than 6.7 Å. Magnetization measurements show the presence of 3D antiferromagnetic ordering below TN with the existence of a noticeable magneto-crystalline anisotropy. From low-temperature neutron diffraction data, it can be observed that the existence of antiferromagnetic order is originated by the antiparallel ordering of ferromagnetic layers of [FeBr4](-) metal complex along the b direction. The magnetic unit cell is the same as the chemical one, and the magnetic moments are aligned along the c direction. The DFT calculations reflect the fact that the spin density of the iron ions spreads over the bromine atoms. In addition, the projected density of states (PDOS) of the imidazolium with the bromines of a [FeBr4](-) metal complex confirms the existence of the anion-π interaction. Magneto-structural correlations give no evidence for direct iron-iron interactions, corroborating that the 3D magnetic ordering takes place via superexchange coupling, the Fe-Br···Br-Fe interplane interaction being defined as the main exchange pathway.